Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor. The rotor is coupled to the nacelle and includes a rotatable hub having one or more rotor blades. The rotor blades are connected to the hub by a blade root. The rotor blades capture kinetic energy from wind using known airfoil principles and convert the kinetic energy into mechanical energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The particular size of the rotor blades is a significant factor contributing to the overall capacity of the wind turbine. Specifically, increases in the length or span of a rotor blade may generally lead to an overall increase in the energy production of a wind turbine. Accordingly, efforts to increase the size of rotor blades aid in the continuing growth of wind turbine technology and the adoption of wind energy as an alternative and commercially competitive energy source. Such increases in rotor blade size, however, may impose increased loads on various wind turbine components. For example, larger rotor blades may experience increased stresses at the connection between the blade root and the hub, leading to challenging design constraints, both characterized by extreme events and fatigue life requirements.
The likelihood of structural failure due to fatigue at the rotor blade joint is typically increased by the presence of high stress concentration between the load bearing components, manufacturing defects, unexpected loading events, or deterioration of the joint. Loss of preload can also occur in the bolted joint which is known to reduce fatigue life. To endure the load envelope specific to the rotor blade root, various methods and systems have been devised and implemented to improve the connection between the dissimilar materials intrinsic to the rotor components. For example, some systems consist of a blade root having a flange, wherein the flange is bolted to the hub. In other systems, a threaded insert is bonded or infused within the blade root laminate and a bolt (i.e. the load bearing component) is screwed therein. In still additional systems, low-cost, low-density foam is inserted between the bolts and the blade root laminate. Such systems, however, are not directed to a blade root having a T-bolt connection.
Thus, there is a need for a rotor blade assembly having improved stiffness that is directed to a blade root having a T-bolt connection. Accordingly, a rotor blade assembly having a rigid root insert compressed by the T-bolt connection and thereby providing improved blade root stiffness would be advantageous.